A mother liquor circulation device for alumina powder

Abstract

This invention discloses a mother liquor circulation device for alumina powder, relating to the field of alumina processing. It includes a pretreatment box and a pretreatment tank located below the pretreatment box. The inner wall of the pretreatment tank is equipped with heating elements. The pretreatment box has a processing chamber inside, with two sets of magnetic separation belts symmetrically installed on both sides of the inner wall of the processing chamber. A feed inlet is installed at the top of the pretreatment box, and a drain box is installed at the bottom of the feed inlet. Drainage channels are symmetrically located on both sides of the drain box. A slow-flow box is installed on the inner wall of the processing chamber below the magnetic separation belts, with the bottom of the magnetic separation belts extending to the bottom of the slow-flow box. This mother liquor circulation device for alumina powder reduces the amount of scale formation in subsequent leaching processes by pre-removing titanium and silicon minerals contained in the circulating mother liquor, thereby avoiding the formation of sodium silicate slag and alkali loss.

Description

Technical Field

[0001] This invention relates to alumina processing technology, specifically to a mother liquor circulation device for alumina powder. Background Technology

[0002] In alumina production, the Bayer process has become the mainstream technology due to its simple process and wide adaptability. The mother liquor circulation system is the core carrier throughout the entire process, and the leaching process, as the starting point of the mother liquor circulation, undertakes the core task of efficient alumina leaching from bauxite. Its operating efficiency directly determines the basic properties of the mother liquor and the overall operating tone of subsequent processes. With the increasing depletion of high-quality bauxite resources, the current alumina industry has to use a large amount of difficult-to-process bauxite with high titanium, high silicon, and high organic matter content (such as the Tianshengqiao mining area in Yunnan Province, my country, where the titanium mineral content is as high as 10% or more and the silicon dioxide content is over 10%). This has led to increasingly prominent technical bottlenecks in the leaching process. Not only has its own leaching efficiency, equipment stability, and operating economy continued to deteriorate, but impurities and process defects are also transmitted downstream through the mother liquor circulation, becoming the core problem restricting the efficient and green development of the entire production system.

[0003] In the high-temperature and high-pressure leaching environment, titanium minerals (anatase, rutile, etc.) in bauxite react with caustic alkali and lime in a series of reactions, forming a synergistic deterioration effect: the rapid reaction of titanium minerals generates dense and hard sodium titanate / calcium titanate scale, which tightly covers the heat exchange tube bundles of the preheater and pressure cooker, resulting in a significant decrease in heat transfer coefficient, a surge in steam consumption, and a shortening of the equipment pickling cycle to 15-20 days. Frequent shutdowns severely disrupt production continuity. At the same time, the reaction of titanium minerals inhibits alumina leaching, reducing the leaching rate to below 50%. Unreacted fine titanium slag is suspended in the mother liquor and circulates and accumulates, further aggravating the risk of scaling. Silica minerals react with caustic alkali to form sodium silicate slag (Na2O・Al2O3・2SiO2・2H2O), which is the core reason for the surge in alkali consumption (the sodium-silicon ratio N / S in red mud of alumina plants in my country is generally 0.28-0.35). Although lime can convert it into hydrated garnet, the carbon-alkali (Na2CO3) accumulated in the mother liquor will destroy its stability, resulting in persistently high alkali consumption. Moreover, the reaction selectivity of silica minerals varies greatly, and local reaction imbalances are prone to occur when temperature and pressure fluctuate. The fine-grained sodium silicate slag and hydrated garnet will increase the viscosity of the system, reduce the penetration capacity of the alkali solution, and further deteriorate the leaching efficiency.

[0004] For example, the Chinese invention patent CN121102980A discloses an alumina production mother liquor recycling device, which significantly improves the cleaning efficiency of the filter plate surface and shortens the single filtration cycle by optimizing the backwashing structure of the leaf filter. However, in practical applications, the backwashing cleaning ability of the leaf filter plate can only solve the problem of "filter surface contamination" and cannot fundamentally improve the impurity composition of the mother liquor itself.

[0005] Because the circulating mother liquor in the leaching process contains a large amount of titanium and silicon minerals, under high-temperature and high-alkali leaching conditions, titanium minerals easily react with alkaline solutions to form fine sodium titanate or calcium titanate particles, while silicon minerals easily form sodium silicate slag or fine hydrated garnet crystals. As these solid impurities continuously circulate with the mother liquor, they will continue to be generated, agglomerate, or recrystallize during the continuous leaching process, maintaining a high level of fine-particle impurities in the mother liquor.

[0006] Therefore, even with high backwashing efficiency, leaf filters still struggle to completely handle the large amount of fine impurities continuously formed by titanium and silicon minerals during circulation. The continuous influx of fine particulate impurities into subsequent fine filtration stages easily leads to rapid adsorption on the filter membrane surface, pore blockage, and a decrease in filtration flux, resulting in a persistently high fine filtration load and ultimately affecting the stability and operational efficiency of the entire mother liquor circulation system.

[0007] This means that simply improving the backwashing efficiency of the leaf filter cannot solve the problem of titanium and silicon minerals generated by the leaching process itself, nor can it prevent the continuous generation of new scale precursors and fine impurities in the circulation. Therefore, the impurity pressure faced by the fine filtration process is still enormous, and it is urgent to carry out systematic control from the source of the leaching process. Summary of the Invention

[0008] The purpose of this invention is to provide a mother liquor circulation device for alumina powder to overcome the above-mentioned shortcomings in the prior art.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a mother liquor circulation device for alumina powder, comprising a pretreatment tank and a pretreatment tank disposed below the pretreatment tank, wherein an electric heating element is disposed on the inner wall of the pretreatment tank; The pretreatment box has a processing chamber inside. Two sets of magnetic separation belts are symmetrically installed on both sides of the inner wall of the processing chamber. A feed inlet is installed on the top of the pretreatment box. A drain box is installed at the bottom of the feed inlet. Drain grooves are symmetrically opened on both sides of the drain box. A slow flow box is installed on the inner wall of the processing chamber below the magnetic separation belts. The bottom of the magnetic separation belts extends to the bottom of the slow flow box. A drain pipe is connected to the bottom of the processing chamber. The drain pipe is spirally arranged and a heat exchange sleeve is fitted on the outside of the drain pipe. The pretreatment tank is divided into a front section and a rear section by a partition. The front section is equipped with multiple sets of first agitators at intervals, and the rear section is equipped with a second agitator. A baffle plate group is set between adjacent first agitators. A discharge box located inside the pretreatment tank is installed at the bottom of the drain pipe. Seed slurry discharge pipe and modified calcium-based agent discharge pipe are respectively installed on the inner wall of the front section and the inner wall of the rear section.

[0010] Furthermore, the magnetic separation belt assembly includes five belt rollers spaced apart on the inner wall of the processing chamber. The belt rollers are driven by a motor. The three belt rollers distributed in a right-angled triangle at the bottom are magnetic rollers, and the two belt rollers horizontally spaced at the top are non-magnetic rollers. The five belt rollers are externally connected to the same magnetic separation belt. The magnetic separation belt includes a direct suction section, a re-suction section, and a discharge section. When the belt rollers rotate, they drive the direct suction sections on both sides of the magnetic separation belt to move upward. The inner wall of the pretreatment tank is provided with strong magnets corresponding to the positions of the direct suction sections, and the position of the drainage tank corresponds to the position of the direct suction section.

[0011] Furthermore, a placement plate is installed on both sides of the inner wall of the processing chamber, and a carrier box is placed on the placement plate. The position and size of the carrier box correspond to the top position of the unloading part. A scraper adapted to the unloading part is installed on the inner wall of the processing chamber. Pick-up and drop-off ports are opened on both sides of the pretreatment box, and magnetic cover plates are provided at the pick-up and drop-off ports.

[0012] Furthermore, the upper and lower ends of the heat exchange sleeve are respectively connected to an inlet circulation pipe and a outlet circulation pipe, and both the inlet circulation pipe and the outlet circulation pipe are connected to the same circulating heat source.

[0013] Furthermore, the seed slurry discharge pipe is located below the discharge box, and the seed slurry discharge pipe has several discharge ports equidistantly opened along its length on the side near the discharge box. A discharge trough is opened below the discharge box. When the discharge trough discharges the circulating mother liquor downwards, the seed slurry sprayed from the discharge port is directly mixed with the downward-flowing circulating mother liquor.

[0014] Furthermore, the seed slurry discharge pipe is connected to an external seed slurry supply source.

[0015] Furthermore, a flow channel is provided between the partition and the bottom of the pretreatment tank. A connecting pipe connected to the downstream section is installed on the outside of the pretreatment tank. The connecting pipe is connected to the leaching equipment. The modified calcium-based agent discharge pipe is located at the bottom of the inner wall of the downstream section and is positioned corresponding to the flow channel. Several discharge holes are equidistantly opened on the surface of the modified calcium-based agent discharge pipe along its length.

[0016] Furthermore, the modified calcium-based agent discharge pipe is connected to an external modified calcium-based agent supply source.

[0017] Furthermore, the flow-blocking plate assembly includes flow-blocking plates spaced apart on both sides of the inner wall of the front section, and a flow-blocking channel is formed between the two flow-blocking plates and the inner walls on both sides of the front section.

[0018] Furthermore, both the first and second stirrers include a drive shaft installed on the inner wall of the pretreatment tank. Multiple sets of vertical stirring blades are installed on the outside of the drive shaft from top to bottom, and inclined stirring blades are installed at the bottom of the outside of the drive shaft. When the drive shaft rotates, the inclined stirring blades push the liquid at the bottom to flow upward.

[0019] Compared with the prior art, the mother liquor circulation device for alumina powder provided by the present invention has the following beneficial effects: 1. The mother liquor circulation device for alumina powder pre-removes titanium and silicon minerals contained in the circulating mother liquor, thereby reducing the amount of scale formation in subsequent leaching processes from the source, and effectively avoiding the formation of sodium silicon slag and reducing alkali consumption loss.

[0020] 2. The mother liquor circulation device for alumina powder adopts a structure of "magnetic rollers with right-angled triangular distribution plus double magnetic separation belt". Through the dual adsorption design of the direct suction section and the re-suction section, combined with the strong magnet to enhance the magnetic field strength, it can accurately capture titanium minerals (anatase, rutile and other strongly magnetic particles) in bauxite slurry, with a removal rate of over 45%, which is far superior to traditional single magnetic separation equipment.

[0021] 3. The mother liquor circulation device for this alumina powder has discharge ports equidistantly spaced along the length of the seed slurry discharge pipe, which are precisely aligned with the unloading trough of the discharge box. This ensures that the seed slurry and circulating mother liquor are mixed synchronously and evenly dispersed. The seed concentration in the first stage is stabilized at 6%-8%, and the efficiency of induced active silicon directional precipitation is improved by 30%. The modified calcium-based agent discharge pipe in the second stage is set close to the flow channel, which can quickly react with the silicon slag generated in the first stage. The conversion rate of hydrated garnet is ≥92%, effectively avoiding the decomposition and redissolution of sodium silicon slag. The alkali consumption (Na2O loss) is reduced to ≤3kg / t-Al2O3, which is more than 70% lower than the traditional process. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0023] Figure 1 This is a schematic diagram of the overall structure provided for an embodiment of the present invention; Figure 2 This is a schematic diagram of the internal structure of the pretreatment box provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the longitudinal cross-sectional structure of the pretreatment box provided in an embodiment of the present invention; Figure 4 Provided for embodiments of the present invention Figure 3Enlarged structural diagram at point A in the middle; Figure 5 This is a schematic diagram of the separation structure between the magnetic cover and the pretreatment box provided in an embodiment of the present invention; Figure 6 This is a schematic diagram of the internal structure of the pretreatment tank provided in an embodiment of the present invention; Figure 7 Provided for embodiments of the present invention Figure 6 Enlarged structural diagram at point B; Figure 8 This is a schematic diagram of the transverse cross-sectional structure of the pretreatment tank provided in an embodiment of the present invention.

[0024] Explanation of reference numerals in the attached figures: 1. Pretreatment box; 101. Inlet; 2. Pretreatment tank; 201. Front section; 202. Rear section; 203. Heating element; 204. Flow channel; 205. Connecting pipe; 3. Drain box; 31. Flow buffer box; 32. Drain pipe; 33. Heat exchange jacket; 34. Inlet circulation pipe; 35. Drain circulation pipe; 36. Drain tank; 4. Baffle; 41. First agitator; 42. Second agitator; 43. Baffle plate assembly; 431. Baffle plate ; 432, flow obstruction channel; 44, discharge box; 441, unloading trough; 45, seed slurry discharge pipe; 451, discharge port; 46, modified calcium-based agent discharge pipe; 5, belt roller; 51, magnetic roller; 52, non-magnetic roller; 53, magnetic separation belt; 531, direct suction section; 532, re-suction section; 533, feeding section; 534, strong magnet; 54, carrier box; 55, scraper; 6, drive shaft; 61, vertical stirring blade; 62, inclined stirring blade. Detailed Implementation

[0025] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0026] Example 1: Please refer to Figures 1-8 A mother liquor circulation device for alumina powder includes a pretreatment tank 1 and a pretreatment tank 2 disposed below the pretreatment tank 1. The inner wall of the pretreatment tank 2 is provided with an electric heating element 203. The pretreatment box 1 has a processing chamber inside. Two sets of magnetic separation belts are symmetrically installed on both sides of the inner wall of the processing chamber. The top of the pretreatment box 1 is equipped with a feed inlet 101. The bottom of the feed inlet 101 is equipped with a drain box 3. Drainage grooves 36 are symmetrically opened on both sides of the drain box 3. The inner wall of the processing chamber is equipped with a slow flow box 31 located below the magnetic separation belts. The bottom of the magnetic separation belts extends to the bottom of the slow flow box 31. The bottom of the processing chamber is connected to a drain pipe 32. The drain pipe 32 is spirally arranged. A heat exchange sleeve 33 is sleeved on the outside of the drain pipe 32. The pretreatment tank 2 is divided into a front section 201 and a rear section 202 by a partition 4. Multiple sets of first agitators 41 are arranged at intervals inside the front section 201, and a second agitator 42 is arranged inside the rear section 202. A baffle plate group 43 is arranged between adjacent first agitators 41. A discharge box 44 located inside the pretreatment tank 2 is installed at the bottom end of the discharge pipe 32. A seed slurry discharge pipe 45 and a modified calcium-based agent discharge pipe 46 are respectively installed on the inner wall of the front section 201 and the inner wall of the rear section 202.

[0027] During operation, the slurry is introduced through the feed inlet 101 and discharged from the drain box 3 onto the magnetic separation belts on both sides. Impurities such as titanium minerals are adsorbed onto the magnetic separation belts and removed. The slurry after titanium mineral removal is transported to the pretreatment tank 2 through the drain pipe 32. In this process, the slurry passing through the drain pipe 32 is heated through the heat exchange sleeve 33.

[0028] After the slurry enters the pretreatment tank 2, it first flows in the front section 201. During this process, the seed slurry is transported as needed through the seed slurry discharge pipe 45, so that it comes into contact with the incoming titanium-removing mineral slurry and catalyzes the active silicon in the titanium-removing mineral slurry to generate silicon slag. During this process, the first agitator 41 works continuously to stir, and the flow rate of the liquid is slowed down by the flow obstruction effect of the baffle plate group 43, which is conducive to the generation of silicon slag.

[0029] After the slurry mixed with silica slag enters the downstream section 202, the modified calcium-based agent is transported through the modified calcium-based agent discharge pipe 46. Under the stirring of the second agitator 42, the silica slag can react with the modified calcium-based agent to generate hydrated garnet.

[0030] Example 2: This example provides a technical solution based on the above example: The magnetic separation belt group includes five belt rollers 5 spaced apart and installed on the inner wall of the processing chamber. The belt rollers 5 are driven by a motor. Among them, the three belt rollers 5 distributed in a right-angled triangle shape at the bottom are magnetic rollers 51, and the two belt rollers 5 horizontally spaced at the top are non-magnetic rollers 52. The five belt rollers 5 are externally connected to the same magnetic separation belt 53.

[0031] The magnetic separator 53 includes a direct suction section 531, a re-suction section 532, and a discharge section 533. When the belt roller 5 rotates, it drives the direct suction section 531 on both sides of the magnetic separator 53 to move upward. The inner wall of the pretreatment tank 2 is provided with a strong magnet 534 corresponding to the position of the direct suction section 531. The position of the discharge tank 36 corresponds to the direct suction section 531, so that the slurry discharged from the discharge tank 36 can first contact the direct suction section 531. Thus, the direct suction section 531 can adsorb the titanium minerals contained in the slurry. Some of the lost titanium minerals are collected in the slow flow box 31 with the slurry. At this time, they can be adsorbed again by the re-suction section 532, so that the removal effect of titanium minerals is better.

[0032] In this embodiment, a placement plate is installed on both sides of the inner wall of the processing chamber, and a carrier box 54 is placed on the placement plate. The position and specifications of the carrier box 54 correspond to the top position of the unloading part 533. The inner wall of the processing chamber is equipped with a scraper 55 that is compatible with the unloading part 533. Both sides of the pretreatment box 1 are provided with pick-up and drop-off ports, and magnetic cover plates are provided at the pick-up and drop-off ports. Magnetic rings are embedded at the pick-up and drop-off ports. The magnetic cover plates are attracted by the magnetic rings, making it more convenient to open and close the pick-up and drop-off ports.

[0033] It should be added that the upper and lower ends of the heat exchanger sleeve 33 are respectively connected to the liquid inlet circulation pipe 34 and the liquid outlet circulation pipe 35. Both the liquid inlet circulation pipe 34 and the liquid outlet circulation pipe 35 are connected to the same circulating heat source. The heat circulation medium here can be the secondary steam generated by the flash tank at the end of the leaching process, which can effectively recover heat and reduce energy consumption.

[0034] Example 3: The seed slurry discharge pipe 45 is located below the discharge box 44, and a plurality of discharge ports 451 are equidistantly opened on the side of the seed slurry discharge pipe 45 near the discharge box 44 along its length direction. A discharge trough 441 is opened below the discharge box 44. When the mother liquor is discharged downward in the discharge trough 441, the seed slurry sprayed out of the discharge port 451 is directly mixed into the downward flowing mother liquor.

[0035] It should be noted that the seed slurry discharge pipe 45 is connected to an external seed slurry supply source. The seed crystals here are recycled by-products, sodium silicate slag / water flower garnet, which are wet-ground to a particle size of ≤40μm by a rod mill / ball mill. Then, a small amount of recycled mother liquor is added and stirred to prepare a silicate slag seed slurry with a concentration of 20%-25%. Finally, the slurry is precisely delivered by a corrosion-resistant metering pump at an addition amount of 6%-8% of the slurry mass.

[0036] In this embodiment, a flow channel 204 is provided between the partition 4 and the bottom of the pretreatment tank 2. A connecting pipe 205 connected to the rear section 202 is installed on the outside of the pretreatment tank 2. The connecting pipe 205 is connected to the leaching equipment. The modified calcium-based agent discharge pipe 46 is located at the bottom of the inner wall of the rear section 202 and its position corresponds to the flow channel 204. Several discharge holes are equidistantly opened on the surface of the modified calcium-based agent discharge pipe 46 along its length direction.

[0037] It should be noted that the modified calcium base agent discharge pipe 46 is connected to an external modified calcium base agent supply source. The modified calcium base agent here is prepared by mixing quicklime and calcium oxide in a mass ratio of 7:3 and grinding them to a particle size of ≤8μm. The amount added is 3%-5% of the mass of bauxite.

[0038] In this embodiment, the flow baffle assembly 43 includes flow baffles 431 spaced apart on both sides of the inner wall of the front section 201. A flow baffle channel 432 is formed between the two flow baffles 431 and the inner walls on both sides of the front section 201, which can effectively slow down the flow rate of the liquid, so that the seed crystal can contact the active silicon and catalyze the formation of silicon slag.

[0039] In this embodiment, both the first stirrer 41 and the second stirrer 42 include a drive shaft 6 installed on the inner wall of the pretreatment tank 2. Multiple sets of vertical stirring blades 61 are installed on the outside of the drive shaft 6 from top to bottom. An inclined stirring blade 62 is installed at the bottom of the drive shaft 6. When the drive shaft 6 rotates, the inclined stirring blades 62 push the liquid at the bottom to flow upward, so that in the front section 201, the precipitation of crystal seeds can be effectively avoided, and the crystal seeds can be evenly distributed in a suspended and dispersed state, ensuring that the crystal seeds are in full contact with the active silicon. In the rear section 202, the silicon slag is fully contacted and reacted with the modified calcium-based agent, thereby effectively promoting the formation of hydrated garnet.

[0040] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A mother liquor circulation device for alumina powder, characterized in that, It includes a pretreatment box (1) and a pretreatment tank (2) located below the pretreatment box (1), wherein the inner wall of the pretreatment tank (2) is provided with an electric heating element (203). The pretreatment box (1) has a processing chamber inside. Two sets of magnetic separation belts are symmetrically installed on both sides of the inner wall of the processing chamber. The top of the pretreatment box (1) is equipped with a feed inlet (101). The bottom of the feed inlet (101) is equipped with a drain box (3). Drainage grooves (36) are symmetrically opened on both sides of the drain box (3). The inner wall of the processing chamber is equipped with a slow flow box (31) located below the magnetic separation belts. The bottom of the magnetic separation belts extends to the bottom of the slow flow box (31). The bottom of the processing chamber is connected to a drain pipe (32). The drain pipe (32) is spirally arranged. A heat exchange sleeve (33) is fitted on the outside of the drain pipe (32). The pretreatment tank (2) is divided into a front section (201) and a rear section (202) by a partition (4). The front section (201) is equipped with multiple sets of first agitators (41) at intervals. The rear section (202) is equipped with a second agitator (42). A baffle plate group (43) is set between adjacent first agitators (41). The bottom end of the drain pipe (32) is equipped with a discharge box (44) located inside the pretreatment tank (2). The inner wall of the front section (201) and the inner wall of the rear section (202) are respectively equipped with a seed slurry discharge pipe (45) and a modified calcium-based agent discharge pipe (46).

2. The mother liquor circulation device for alumina powder according to claim 1, characterized in that, The magnetic separation belt assembly includes five belt rollers (5) spaced apart on the inner wall of the processing chamber. The belt rollers (5) are driven by a motor. The three belt rollers (5) distributed in a right-angled triangle at the bottom are magnetic rollers (51), and the two belt rollers (5) arranged horizontally at the top are non-magnetic rollers (52). The five belt rollers (5) are externally connected to the same magnetic separation belt (53). The magnetic separation belt (53) includes a direct suction part (531), a re-suction part (532), and a discharge part (533). When the belt rollers (5) rotate, they drive the direct suction parts (531) on both sides of the magnetic separation belt (53) to move upward. The inner wall of the pretreatment tank (2) is provided with strong magnets (534) corresponding to the position of the direct suction part (531). The position of the drain tank (36) corresponds to the position of the direct suction part (531).

3. The mother liquor circulation device for alumina powder according to claim 2, characterized in that, Both sides of the inner wall of the processing chamber are equipped with placement plates, and a carrier box (54) is placed on the placement plate. The position and specifications of the carrier box (54) correspond to the top position of the unloading part (533). The inner wall of the processing chamber is equipped with a scraper (55) that is compatible with the unloading part (533). Both sides of the pretreatment box (1) are provided with pick-up and drop-off ports, and magnetic cover plates are provided at the pick-up and drop-off ports.

4. The mother liquor circulation device for alumina powder according to claim 3, characterized in that, The upper and lower ends of the heat exchange sleeve (33) are respectively connected to the liquid inlet circulation pipe (34) and the liquid outlet circulation pipe (35), and the liquid inlet circulation pipe (34) and the liquid outlet circulation pipe (35) are both connected to the same circulating heat source.

5. The mother liquor circulation device for alumina powder according to claim 4, characterized in that, The seed slurry discharge pipe (45) is located below the discharge box (44), and the seed slurry discharge pipe (45) has several discharge ports (451) equidistantly opened along its length on the side near the discharge box (44). A discharge trough (441) is opened below the discharge box (44). When the discharge trough (441) discharges the circulating mother liquor downward, the seed slurry sprayed from the discharge port (451) is directly mixed into the downward flowing circulating mother liquor.

6. The mother liquor circulation device for alumina powder according to claim 5, characterized in that, The seed slurry discharge pipe (45) is connected to an external seed slurry supply source.

7. The mother liquor circulation device for alumina powder according to claim 6, characterized in that, A flow channel (204) is provided between the partition (4) and the bottom of the pretreatment tank (2). A connecting pipe (205) connected to the rear section (202) is installed on the outside of the pretreatment tank (2). The connecting pipe (205) is connected to the leaching equipment. The modified calcium base agent discharge pipe (46) is located at the bottom of the inner wall of the rear section (202) and its position corresponds to the flow channel (204). Several discharge holes are equidistantly opened on the surface of the modified calcium base agent discharge pipe (46) along its length direction.

8. The mother liquor circulation device for alumina powder according to claim 7, characterized in that, The modified calcium base agent discharge pipe (46) is connected to an external modified calcium base agent supply source.

9. A mother liquor circulation device for alumina powder according to claim 8, characterized in that, The baffle plate assembly (43) includes baffle plates (431) spaced apart on both sides of the inner wall of the front section (201), and a baffle channel (432) is formed between the two baffle plates (431) and the inner walls on both sides of the front section (201).

10. A mother liquor circulation device for alumina powder according to claim 9, characterized in that, Both the first stirrer (41) and the second stirrer (42) include a drive shaft (6) installed on the inner wall of the pretreatment tank (2). Multiple sets of vertical stirring blades (61) are installed on the outside of the drive shaft (6) from top to bottom. An inclined stirring blade (62) is installed on the bottom of the drive shaft (6). When the drive shaft (6) rotates, the inclined stirring blade (62) pushes the liquid at the bottom to flow upward.

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